PROJECT SUMMARY/ABSTRACT Immune-mediated nephritis is an important pathogenic determinant in spontaneous lupus and Goodpasture's syndrome (anti-GBM disease), both in mice and in humans. Our recent studies using experimental anti-GBM antibody-induced glomerulai nephritis (AIGN) mouse model have identified tissue kallikreins (klk) as potential disease genes in immune and lupus nephritis and the impaired expression of klk in kidney related with the increased sensitivity to AIGN. Klk genes are encoded within the Sle3 lupus susceptibility interval on chromosome 7 that had previously been associated with spontaneous lupus nephritis. Klks constitute a multi-gene family of serine esterases with a wide spectrum of biological functions. Several nucleotide polymorphisms in the promoter regions of the Klk genes have been identified to be related with the differential expression of kallikreins between AIGN sensitive and resistant mouse strains. Furthermore, the renoprotective effect of kallikrein was proved by two functional experiments: delivering klk1 via adenoviral vector into B.Sle3 mice (AIGN sensitive strain) attenuated the severity of anti-GBM induced nephritis, while blocking kallikrein function in BALB/c mice (AIGN resistant strain) using kinin B2 receptor antagonist (HOE140) rendered these mice sensitive to anti-GBM induced nephritis. Collectively, these studies establish Klk as potential disease genes in anti- GBM disease and lupus nephritis. The current proposal is designed to identify the regulatory elements for the klk upregulation and determine the down-stream molecular pathways related with the enhanced klk expression in kidney tubular cells. A murine model with inducible kidney specific expression of klk will be developed to further assess whether the enhanced klk/kinin signaling in kidney will mediate renoprotection against lupus nephritis induced by Sle1.Sle3 lupus susceptibility loci. PUBLIC HEALTH RELEVANCE: PROJECT NARRATIVE Autoantibody-induced nephritis is largely responsible for the phenotypes of lupus and other autoimmune diseases. Our previous study has proved that antibodies against mouse glomerular basement membrane can increase kallikreins expression in kidney of certain strains of mice and then protect these mice from developing into glomerular nephritis. A better understanding of the molecular mechanism underlying the regulation of kallikreins expression and their potential protective effect on immune nephritis will lead scientists to design better strategies for targeted therapies to treat this disease. This application is to find out why kallikreins are regulated and how they exert protective effect against immune nephritis. Finally we will develop a mouse model in which we can control the kallikreins expression specifically in kidney during specific disease development stage by injecting a reagent named tomaxifen. We will evaluate if the targeted gene therapy will be able to prevent or cure the kidney disease caused by lupus, using this mouse model.